From 16053d9d043dcee4d460417e8c33d65723c6161e Mon Sep 17 00:00:00 2001
From: Ellpeck <me@ellpeck.de>
Date: Sat, 28 May 2022 21:21:25 +0200
Subject: [PATCH] further improve runtime texture packer performance by caching
 the first possible position for a request of a given size

---
 CHANGELOG.md                      |  2 +-
 MLEM.Data/RuntimeTexturePacker.cs | 20 +++++++++++++-------
 Sandbox/GameImpl.cs               |  4 +++-
 3 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index fcce781..faa46f1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -58,7 +58,7 @@ Improvements
 - Premultiply textures when using RawContentManager
 - Allow enumerating all region names of a DataTextureAtlas
 - Cache RuntimeTexturePacker texture data while packing to improve performance
-- Improve RuntimeTexturePacker performance by checking against packed textures in the same order as packing
+- Greatly improved RuntimeTexturePacker performance
 
 Fixes
 - Fixed SoundEffectReader incorrectly claiming it could read ogg and mp3 files
diff --git a/MLEM.Data/RuntimeTexturePacker.cs b/MLEM.Data/RuntimeTexturePacker.cs
index e149c99..630e74c 100644
--- a/MLEM.Data/RuntimeTexturePacker.cs
+++ b/MLEM.Data/RuntimeTexturePacker.cs
@@ -36,6 +36,7 @@ namespace MLEM.Data {
 
         private readonly List<Request> texturesToPack = new List<Request>();
         private readonly List<Request> alreadyPackedTextures = new List<Request>();
+        private readonly Dictionary<Point, Point> firstPossiblePosForSizeCache = new Dictionary<Point, Point>();
         private readonly Dictionary<Texture2D, TextureData> dataCache = new Dictionary<Texture2D, TextureData>();
         private readonly bool autoIncreaseMaxWidth;
         private readonly bool forcePowerOfTwo;
@@ -168,6 +169,8 @@ namespace MLEM.Data {
             var stopwatch = Stopwatch.StartNew();
             foreach (var request in this.texturesToPack.OrderByDescending(t => t.Texture.Width * t.Texture.Height)) {
                 request.PackedArea = this.FindFreeArea(request);
+                // if this is the first position that this request fit in, no other requests of the same size will find a position before it
+                this.firstPossiblePosForSizeCache[request.PackedArea.Size] = request.PackedArea.Location;
                 this.alreadyPackedTextures.Add(request);
             }
             stopwatch.Stop();
@@ -201,9 +204,7 @@ namespace MLEM.Data {
                     request.Texture.Texture.Dispose();
             }
 
-            this.texturesToPack.Clear();
-            this.alreadyPackedTextures.Clear();
-            this.dataCache.Clear();
+            this.ClearTempCollections();
         }
 
         /// <summary>
@@ -212,11 +213,9 @@ namespace MLEM.Data {
         public void Reset() {
             this.PackedTexture?.Dispose();
             this.PackedTexture = null;
-            this.texturesToPack.Clear();
-            this.alreadyPackedTextures.Clear();
-            this.dataCache.Clear();
             this.LastCalculationTime = TimeSpan.Zero;
             this.LastPackTime = TimeSpan.Zero;
+            this.ClearTempCollections();
         }
 
         /// <summary>Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.</summary>
@@ -229,7 +228,7 @@ namespace MLEM.Data {
             size.X += request.Padding * 2;
             size.Y += request.Padding * 2;
 
-            var pos = new Point(0, 0);
+            var pos = this.firstPossiblePosForSizeCache.TryGetValue(size, out var first) ? first : Point.Zero;
             var lowestY = int.MaxValue;
             while (true) {
                 var intersected = false;
@@ -294,6 +293,13 @@ namespace MLEM.Data {
             return true;
         }
 
+        private void ClearTempCollections() {
+            this.texturesToPack.Clear();
+            this.alreadyPackedTextures.Clear();
+            this.firstPossiblePosForSizeCache.Clear();
+            this.dataCache.Clear();
+        }
+
         private static int ToPowerOfTwo(int value) {
             var ret = 1;
             while (ret < value)
diff --git a/Sandbox/GameImpl.cs b/Sandbox/GameImpl.cs
index bc14fb6..70fd655 100644
--- a/Sandbox/GameImpl.cs
+++ b/Sandbox/GameImpl.cs
@@ -329,7 +329,9 @@ namespace Sandbox {
                 Console.WriteLine($"Returned {r.Count} regions: {string.Join(", ", r.Select(kv => kv.Key + ": " + kv.Value.Area))}");
             }, 1, true);
             packer.Pack(this.GraphicsDevice);
-            packer.PackedTexture.SaveAsPng(File.Create("_Packed.png"), packer.PackedTexture.Width, packer.PackedTexture.Height);
+
+            using (var stream = File.Create("_Packed.png"))
+                packer.PackedTexture.SaveAsPng(stream, packer.PackedTexture.Width, packer.PackedTexture.Height);
 
             this.OnDraw += (g, t) => {
                 this.SpriteBatch.Begin(samplerState: SamplerState.PointClamp);